1. Field of the Invention
The present invention relates to rubber compositions having strong adhesive force to various rubbers including vulcanized polyolefin rubbers and, adhesives as well as primers comprising the rubber compositions.
2. Description of the Related Art
As rubbers for industrial use, various synthetic rubbers such as polyolefin rubber, styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), isobutylene-isoprene copolymer rubber (IIR), polychloroprene rubber (CR), acrylonitrile-butadiene copolymer rubber (NBR), polyisoprene rubber (IR), etc. or natural rubber (NR) are employed.
Among them, vulcanized polyolefin rubbers represented by ethylene-propylene-diene terpolymer rubber (EPDM) and ethylene-propylene copolymer rubber (EPM) possess many superior properties that are excellent in weather resistance, aging resistance and resistance to ozon, provide a wide temperature range for use from -50.degree. to 150.degree. C., and the like. Therefore, vulcanized polyolefin rubbers have now been used in many fileds of industry, including rubber parts for automobiles such as weatherstrips, glass run, moldings, etc.
On the other hand, it is known that the aforesaid vulcanized polyolefin rubbers such as EPDM, EPM, etc. contain no polar group in the main chain of the molecule thereof so that even though paints or adhesives are applied to the surface thereof, the resulting coating are liable to be stripped off.
For this reason, it is extremely difficult under the present situations to (1) coat the surface of the vulcanized polyolefin rubbers, (2) adhere the vulcanized polyolefin rubbers to each other and (3) adhere the vulcanized polyolefin rubbers to synthetic resins or metals.
Various measures for overcoming these difficulties have been attempted but no satisfactory solution has not been found yet.
As an example, the aforesaid weatherstrips are used as sealing agents for front or rear reveal portions, door portions or trunk portions, where the weatherstrips are mounted in different manners depending upon place to be used.
Namely, in the case of the trunk portions, a method which comprises mounting weatherstrips obtained by previously extrusion-molding, coating adhesives at the edges thereof and adhering, around a trunk opening of the body is adopted.
Further in the case of the reveals, there are adopted a method which comprises subjecting reinforced glass coated with an adhesive and a weatherstrip to one-piece molding, a method which comprises inserting a weatherstrip obtained by previously extrusion-molding and adhering the edges thereof by a vulcanizing adhesion method around reinforced glass, etc.
However, the aforesaid vulcanized polyolefin rubbers such as EPDM, EPM, etc. have poor adhesion to adhesives or paints so that upon coating adhesives at the edges of weatherstrips composed of the vulcanized polyolefin rubbers, various pre-treatments must be made on the surface of the weatherstrip.
However, even though such pre-treatments are made, adhesive property at the adhered portion has come to be actually deteriorated due to the use over a long period of time.